Arctic char in Dillon Reservoir could enhance lake as top fishing destination

Biologists from Colorado State University’s Warner College of Natural Resources are studying the food web of Dillon Reservoir in Summit County, to enhance the aquatic ecosystem to support the Arctic char.

Arctic char are prized by fishermen around the world as a beautiful, good-fighting sportfish that can grow to more than 20 pounds in the depths of cold, freshwater lakes. Dillon Reservoir is the only public destination in the lower 48 states, outside of Maine, where anglers can have a chance to land the fish.

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As freezing temperatures sweep through Summit County, one aquatic creature is actually thriving.

The Arctic char is showing signs of success in Dillon Reservoir, according to a study conducted by a team of researchers from Colorado State University. Typically found only in Arctic waters, this cold-water fish — a species of trout — could help turn the reservoir into an angler’s paradise.

Brett Johnson, fisheries biology professor at the Warner College of Natural Resources at CSU, led the research initiative. Johnson is developing models to improve the ecosystem of Dillon Reservoir and enhance the lake as a fishing destination.

“The Dillon Reservoir is a high-profile resource, located on the interstate, around many resort towns,” he said. “Yet it’s had a fairly lackluster reputation as a fishery for a long time. It’s difficult to manage fish there — it’s cold and there are a lot of shrimp.”

The mysis shrimp was introduced into Dillon Reservoir in 1970 as a food source to fatten trout and salmon. But the small nocturnal crustaceans missed the trout’s daytime feeding patterns and began eating all of the zooplankton — leaving salmon and trout hungry and small. The CSU research project focused on a comprehensive study of the lake’s ecosystem, with a goal of restoring balance. As Denver’s largest single water supply source, the reservoir is held to strict nutrient standards.

“The biggest surprise was that we determined the char in there were reproducing naturally,” Johnson said. “One-third of the sample of fish we used for our study were a result of natural reproduction in the reservoir. That stocking program has been very successful.”

The Arctic char was introduced to the reservoir in 1990 to see if they would feed on the shrimp — a main part of their diet. Johnson was curious about how successful the stocking program had been so far. Colorado Parks and Wildlife manages the fishery; Arctic char was stocked in Dillon in 1990, 1992, 1996, 1998 and 2008 to 2011. The reservoir is the only public fishery in the lower 48 states outside of Maine where anglers have a chance of landing the prized fish.

“A lot of anglers don’t even know the char is there; it’s a deep-water fish and it’s such a big system — they’re hard to catch,” Johnson said.

Brad Eckert, resource specialist at Summit County Open Space and Trails, said Summit County’s role in this project is served through the Dillon Reservoir Recreation Committee, a committee that manages the Dillon Reservoir Recreation Area, which includes the surface of Dillon Reservoir and many of its adjacent properties. The committee comprises Denver Water, the towns of Dillon and Frisco, the U.S. Forest Service and Summit County Government.

Travis Thompson, spokesman for Denver Water, said his company values recreation throughout Colorado’s watersheds and supports the effort to boost the diversity of fishing opportunities at Dillon Reservoir.

“We continue to work with Colorado Parks and Wildlife to manage and ensure fish habitats at our reservoirs thrive, and are excited about this project to restore balance of the fishery at Dillon,” he said.

After three years of study, Johnson’s research team — which also includes CSU fishery biology master’s student Devin Olsen, Parks and Wildlife biologist Jon Ewert and scientist and financier Douglas Silver — believes the notion of a committed stocking effort of Arctic char holds promise.

The Dillon Reservoir Recreation Committee “is anticipating the impact to be positive, with the Arctic char attracting more anglers to Dillon,” Eckert said. “The (char) could provide a valuable ‘boutique fishery,’ or a unique angling experience.”

Eckert said the impacts to the environment and ecosystem are also anticipated to be positive.

There is no cost to the recreation committee for the stocking, nor is there any cost for the research projects. An update from CSU will be provided to the committee at an April 15 meeting.